#include "fe.h"
#include "crypto_additions.h"

void ge_p3_to_montx(fe u, const ge_p3 *ed) {
    /*
       u = (y + 1) / (1 - y)
       or
       u = (y + z) / (z - y)

       NOTE: y=1 is converted to u=0 since fe_invert is mod-exp
    */

    fe y_plus_one, one_minus_y, inv_one_minus_y;

    fe_add(y_plus_one, ed->Y, ed->Z);
    fe_sub(one_minus_y, ed->Z, ed->Y);
    fe_invert(inv_one_minus_y, one_minus_y);
    fe_mul(u, y_plus_one, inv_one_minus_y);
}

